Process for controlling the concentrations of suspensions



Apnl 24, 1951 F. J. FONTEIN PROCESS FOR CONTROLLING THE CONCENTRATIONS OF SUSPENSIONS Filed Aug. 14, 1946 Milli??? Ikeerk IEDZ'GU'IL,

Patented Apr. 24, 1951 p i1 PROCESS FOR CONTROLLING THE CON- CENTRATIONS F SUSPENSIONS Freerk J. Fontein, Heerlen, Netherlands, assignor to De Directie van de Staatsmijnen in Limburg, Heerlen, Netherlands r Application August 14, 1946, Serial No 690,550 In the Netherlands August 28, 1945 This invention relates to process and apparatus for the separation of a suspension into two fractions of controllable concentration, using a cy clone.

It has heretofore been known tocontrol the concentration of the fractions separated by a cyclone by a suitable choice of diameters of the outlet openings of the cyclone. However, these cyclones are ordinarily relatively small and the apex opening through which the heavier fraction is discharged may have a normal diameter as small as or smaller than A of an inch. Consequently there is the constant danger of clogging or unduly narrowing the apex opening. In the case of a cyclone used to thicken separating suspensions such as are used in the sink-float type of washing boxes, such a clogging or narrowing immediately affects the separating action since the lighter fraction will immediately increase in concentration with the resultant loss of solid constituents from the apex discharge.

It is the object of the present invention the resistance being adjusted, for example, by

withdrawal from the body at a certain rate. In terms of apparatus, a closed receiver is associated with the apex opening of the cyclone, the receiver being filled with suspension and having a controllable outlet. If the capacity of the receiver outlet is increased, the pressure in the receiver decreases and the concentration of the suspension leaving the cyclone at its apex also decreases. This results, with some retardation, in the decrease of the concentration of the suspension discharging from the receiver outlet so that the specific gravity of discharge of the whole installation decreases. On the other hand, if the capacity of the receiver outlet is diminished, then pressure in the receiver increases and the concentration of the suspension leaving the cyclone at its apex increases, with the result, with some retardation, of the increase of concentration of the suspension discharging from the receiver so that the specific gravity of discharge of the whole installation increases. The advantages arising from the practice of the invention are especially notable when a number of cyclones are associated with a common receiver.

Apparatus suitable for the practice of the invention is shown by Way of example in the 1 Claim. (01. 209 -211) a overcome this difliculty; In accordance with the comprising two cyclones associated with a common receiver and l I Figure 2 is a fragmentary axial sectionpf a receiver with another form of discharge control means.

Referring to Figure 1, reference numeral 5 designates a cyclone comprising a shallow'cylindrical top portion 6 having an inlet opening! at the end of a tangentially directed feed pipe 8. A cover plate 9 is secured to the top of portion 6 and has a central discharge opening Ill. Reference numeral ll designates a conicalportion depending from portion 6 coaxially therewith and having an apex opening I2 aligned with the base opening l0. As here shown, the lower end of portion I I is flanged at [3 and is secured to the top wall [4 of a closed receiver or tank [5 which has an opening 16 registering with the apex opening l2.' The receiver has a conical body portion I! which terminates downwardly in a housing l8 for a star wheel l9 adapted to be driven at a controllable speed for controlling the rate of discharge from the receiver.

Reference numeral 2|] designates a cyclone like cyclone 5 and similarly associated with the receiver.

In the operation of the apparatus, the liquid suspension to be thickened is fed to the cyclones through the feed pipes 8. The infed suspension will move in inner and outer vortices having the same rotational sense. However, the inner vortex moves axially toward the base discharge opening III while the outer vortex moves axially toward apex opening l2. The fraction of higher concentration leaves the outer vortex of each cyclone through the apex opening I2 and the fraction of lower concentration leaves the inner vortex of each cyclone through the base opening l0. When the receiver is filled by the apex discharges, the star wheel is rotated at a speed to maintain the desired pressure in the receiver and, hence, the desired resistance to the entry of the apex discharges. It will be observed that receiver l5 thus defines a pressure zone.

The advantage of providing a plurality of small cyclones instead of a single large one is that the precipitation efficiency of the small cyclone is greater, and this efiiciency does not decrease as much as that of the larger cyclone when the specific gravity of the apex discharge increases. Hitherto the lower limit of the cyclone size has been determined principally by the size of the apex aperture which decreases in proportion to the size of the cyclone. However, if several small cyclones discharge into a single suspensionfilled receiver, the specific gravity of the discharge is no longer determined by the size of the apex of the cyclone but by the pressure in the receiver and, consequently, the size of the apex openings can be large enough so as to eliminate the danger f clogging.

The average capacity of the receiver outlet is, of course, independent of the number of cyclones and only dependent upon the capacity of the installation, and this average outlet capacity will be the same in the case 'of a single large cyclone or a number of small cyclones discharging into the receiver. Furthermore, it'isobvious- The thickening of 550 gallons per hour of a loess suspension from aIsink-fioat coal washing plant drom an average specific gravity :of 1:06 to an average specific gravity of :1.6 can :be accomplished in ma single cyclone having a top diameter of one foot, an inside feed gpipe :diameter of 2 inches, a base outlet diameter of 2 inches, and an apex-outletidiameter -of 'of :an inch average. The lossof solid -.constituents in the suspension leaving through the base opening of the cyclone amounts to 50%, that is, :about one ton per hour. Similarly thickening the same quantity of suspension in six cyclones discharginginto a common receiver filled withsuspension up to the same specific gravity, the maximum diameter of .the cyclones is 2% inches, inlet diameter inch, diameter base-outlet inch, anddiameter of the apex outlet :inch. The capacity of the receiver outlet is equivalent to a diameter of 1% inches, and the loss (if solid constituents through the :base outlets 01 the cyclones'amounts to 25% or .5-ton per hour:

The receiver discharge'can becontrolled-in-any suitable manner. For example, instead of the rotary star wheel of Figure 1, I'may usea :valve 2|, Figure 2, secured to the lower 43nd of the receiver 11', the valve preferably being designed to permit as smooth a flow as possible.

'-Other variations in the form and-arrangement in a liquid into fractions so that the desired fraction will be thickened to have a predetermined concentration value, comprising simultaneously feeding the suspension tangentially to the base area of a plurality of conical spaces and compelling it to move in each of said spaces in .inner :and outer vortices having the same rotational sense but of opposite axial directions,

-1c'ontinu0usly withdrawing a part of the suspension from the inner vortices and discharging it 'axiallylfrom the center of the base end of each conical space to thereby obtain a fraction from each space 'havingra relatively low concentration value, scontinuously withdrawing a part of the suspension from the outer vortex at the apex Aof-eachmonical space to thereby obtain a desired ;fraction having a relatively high concentration value and discharging the last-mentioned fraction from the apices of the conical spaces directly into a larger confined pressure zone surrounding the apex discharges :of the conical rspaces sand filled with :the desired ifracti'on, withdrawing the last-mentioned fraction from .a portion 11f the pressure zone remote from the apex discharges of the conical spaces:andcontroliingthe pressure in the pressure zone by controlling the rate .of withdrawal of the desired fraction from the pressure zone to therebyobtainithe desired concentration of solids .in the :discharge from ithe apices of the conical spaces.

FREERK J. EFONTEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 453,105 Bretney ZMay '26,..1391 1,919,653 I-Iill July '25, 1933 2,102,525 Freeman Dec. 14, 1937 2,273,271 ,Kerns Feb. 17, 1942 2,356,648 Brusset Aug.j22, 1944 LO'IHER REFERENCES The Colliery Guardian, 30 Furnival Street, HolbornE. C. 4, -London,-vol.'CLIX, Nov. 24,1939, page 750, and vol. CLVIIIQMay 12, 1939, page 832. (Copy available in the Scientific Library, U. "S. Patent 'O'filce.) 

